My style when attacking with hook uses a lot of inner tricep, back and side - and can often be painful if it is stopped. If your bicep is strong and you are locked in and patient it is sometimes easier to defend for a while, then pick your moment to hit back. I think the transition from defensive hook to attacking hook is far quicker therefore I would favour the bicep and patience. (also wrist and fingers so you are not rolled out) Paul, Dean, Nick may explain it better.
